Hydrostatic transmissions are commonly used in small riding tractors and the output of the hydrostatic transmission is transmitted to the input member or housing of a differential, while the output shafts of the differential are connected to the tractor drive wheels. Without a differential, both drive wheels will continually rotate at the same speed, which can cause scalping of the lawn when the tractor is moved in a tight turn. However, with the use of a differential, the drive wheel that encounters the least resistance will operate at the greatest speed. For example, if the tractor is moving in a straight path across a hill, the uphill wheel will have less resistance and therefore will operate at the greatest speed. This can cause spinning of the uphill wheel and possible scuffing of the lawn.
Drive systems have been used in the past, such as shown in the U.S. Pat. Nos. 3,190,385 and 3,335,808, in which rotation of the steering column acts to increase the speed of one drive wheel when cornering, while decreasing the speed of the other drive wheel.